The invention relates to a bobbin supporting textile strands, especially synthetic, textured filament yarns to be subjected to a heat and/or wet treatment, the bobbin having an outer, cylindrical or slightly conical grating, the outer side of which forms the curved outer surface of the bobbin serving as a supporting surface for the strands or for a resilient support for the strands, and whereby the bobbin is resiliently compressible both in the axial and in the radial direction.
Several processes, whereby textile strands wound on bobbins are treated, necessitate the possibility of allowing the strands to relax and shrink. This feature applies especially to heat and/or wet treatments of synthetic, textured filament yarns, e.g. at heat shrinking and at dyeing of said yarns. Such processes are in general carried out with the yarns wound on particular shrinking bobbins which simultaneously must be both axially and radially compressible.
Several bobbins of thermoplastic material are known which are compressible in the axial and radial directions, but these bobbins are all encumbered with the draw-back that with heat and/or wet treatments they undergo a plastic deformation, which in practice implies that they are only suitable for a single or a few uses, which makes them much too expensive to use.
In addition, bobbins of plastics are known, which are axially and radially compressible, but which require the use of an inner carrying means such as a mandrel during the winding of the yarn in order to avoid axial and radial compressions during the winding.
Moreover for instance British patent specification No. 1,363,363 and U.S. Pat. No. 2,818,222 disclose axially compressible bobbins of steel. These bobbins have a core of a helical pressure spring surrounded by a helically positioned net or grating of windings and a grating of parallel, axially oriented ribs or lamellas. In both cases these ribs or lamellas can slide on the windings of the helical spring and on guide rings, respectively, during the axial compressions and resilient returning movements of the bobbins. None of these bobbins are, however, radially compressible.
British patent specification No. 1,363,363 discloses, however, also a bobbin of the type shown in the specification which is modified in such a manner that it is both axially and radially compressible. This axial and radial compression is allowed by the windings of lacing wire positioned about the windings of the helical spring being provided with a greating winding width measured in the radial direction of the bobbin so that the lacing windings are movable in and out in the radial direction of the bobbin about the windings of the helical spring. The grating of lacing wire inserted in this manner does possess a certain resilience ensuring that the grating is outwardly displaced on the bobbin in the non-wound state of the bobbin, whereby the inner lacing windings abut the inner side of the windings of the helical spring. The resilient tensions in the lacing wire ensuring this feature are, however, so insignificant that during the winding of yarn on the bobbin, a mandrel must be used inside the bobbin, said mandrel ensuring that the lacing wire is kept in its outer position. The latter procedure involves additional work and is more expensive. In addition, the removal of the mandrel upon termination of the winding implies that the lacing wire is pressed inwards again by the yarns in such a manner that during the further handling of the bobbins said yarns are too badly retained on the bobbins and sometimes slide off said bobbins. A need thus exists for amending these bobbins in such a manner that they can be used during and after the winding without a mandrel, but with an outwardly displaced lacing wire as long as it is desired.